Mariah Carey cancels Vegas show

Mariah Carey just started her Las Vegas residency last week.

And now she's having to cancel tonight's show.

The songstress says in an Instagram post that bronchitis is to blame.

"Hey guys," she wrote on Instagram. "I've been fighting bronchitis for the past few days.. almost better but on mandatory vocal rest per doctor's orders."I'm so sorry to cancel tonight's show but I promise to make it up to you!!!"

She signed it: "Love you always, MC"

Carey has been busy this week, according to her Instagram account, also shooting the new video for Infinity with buddy Brett Ratner.

She's scheduled to perform at Sunday's Billboard Music Awards, airing live on ABC.